Abstract

Surface atomic steps in unpassivated copper lines under electromigration (EM) have been directly observed in ultrahigh vacuum by in situtransmission electron microscopy (in situTEM). The combination of {111} planes and ⟨110⟩ directions for crystalline Cu were found to be the most favored EM paths. The in situTEM study of EM-induced evolution of Cusurface structures provides a sound basis for understanding the dependence of EM-induced atomic migration mechanism on crystal orientation of crystalline Cu. The understanding shall lead to the effective strategy of using appropriate passivation layer to suppress the electromigration.